Electric heater



Oct. 23, 1923.

A. N. OTIS ELECTRIC HEATER 2 Sheets-Sheet 1 Filed April 2, 1 921 Inventor: Alb Tb n Otis.

His Attorney.

Oct. 23, 1923. 1 1,471,913

A. N. OTlS ELECTRI C HEATER Filed April 2; 1921 2 Sheets-Sheet 2 Fig. 5.

Inventor Albert Tl; Otis,

P Has Attcrney.

Patented Oct. 23, 1923.

UNITED STATES v 1,471,913 PATENT OFFICE.

ALBERT N. OTIS, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC HEATER.

Application filed April 2, 1921. Serial 110,458,007.

T all whom it may concern:

Be it known that I, ALBERT N. (has, a citizen of the United States, residing at Schenectady, in the county of Schenectady,

State of New York, have invented certain new and useful Im rovements in Electric Heaters, of which t 1e following is a specification.

My invention relates to electric heaters and has for its object the provision of an improved device of this character, having a rugged construction and being reliable and eflicient in operation.

More specifically my invention. relates to electric resistance heaters for steam boilers, liquid heaters of various kinds, and the like. The heating of steam boilers by electricity has many advantages. There is no necessity for the handling of coal and ashes, no

, brick setting or smoke stack is required, and

the boiler and eq i ment occupy but very little floor space. he boiler may be located at the most advantageous point to reduce the length of the pipe lines and heat losses therein, and it can be entirely covered with heat insulating material so as to reduce the heat losses in the boiler itself to an almost negligible amount; therefore, the efiiciency of the steam system is greatly increased. My invention has the advantage that it can be applied to fire tube boilers and liquid heaters as already built. In localities where the electric ower consumption is very low during certain periods of the day or night, steam can be stored in suitable heat insulated tanks or containers for use during periods of heavy load so as to take advantage of the inducement of lower power rates usually offered during such periods of light load.

I :In carrying out my invention, I employ aheating unit consisting of a ribbon of suitable resistance alloy which is folded or bent in the she. e of a hairpin so as to have two substantia ly parallel portions which are provided with spacing and supporting insulators of such size that the unit when it is assembled may he slipped freely into the tubes of a fire tube boiler. The unit is placed in the tube so that the sides of the resistance ribbon are vertical. As thus positioned the ribbon is to a large degree selfsupporting; this is a great advantage for the heat radiation to the tube need be obstructed at intervals only by spacing and supporting insulators. By constructing the heating element in the form of a ribbon, a large heat radiat-ing'surface is obtained. The double heating effect of two elements in each tube is obtained by folding the element, while at the same time any possibility of induction in the tube or other parts of the boiler is eliminated, the terminals of the element are conveniently adjacent each other, and a ri id, stifi heating unit which resists any tendency to bend from contraction or expansion due to changes in temper ature is obtained by clamping the parallel portions of the element together. By eliminating induction, I have provided a heater which can be 0 erated' at unity power factor, thus provi ing a very desirable load.

In the accompanying drawings, Fig. 1 is an elevation view, partly in cross section, showing the application of my invention to a fire tube boiler; Fig. 2 is a vertical section of Fig. 1'; Fig. 3 is a View, partly in cross section, showing the details of the heating unit; Fig. 4 is a perspective view of a section of the heating unit, showing the spacing and supporting insulators; while Figs. 5 and 6 show a modification of my invention.

Referring to Figs. 1 and 2 of the drawings, the boiler 10 1s supported by means of saddles 11 on concrete piers 12, only one of which is shown. The cylindrical portion of the boiler is completely covered by a jacket 13 of suitable heat insulating material. At one end of the boiler between the doors 14 and thehead 15 is a chamber 16 which provides space for the terminal connections for the heating units. In each tube 17 of the boiler is a heating unit 18.

As shown in Figs. 3 and 4, the heating element consists of a ribbon made of a suitable resistance alloy which is folded or bent to form two parallel portions 19 and 20 and inserted in the tube so that its sides are. vertical and its ends protrude adjacent each other. The folded portions of the heating element are spaced at intervals by means of cooperating insulating clamps 21, made of a suitable electrically insulating material, which are clamped tightly upon the parallel portions of the heating element bymeans of a screw 22 and nut (not shown) so as to hold the portions of the heating ele ment spaced apart in slots in the inner faces of the clamps. Preferably, the spacin clamps are attached in sets of two locate near each'other s0 as to hold in place between them a supporting insulator 23, having a square hole. The insulator is slipped over the heating element, and it is just so large that it can be inserted loosely in the tube. The supporting insulator holds the heating element in a central position in the.

site pairs of outwardly extending loops or.

projections 35 in the ribbon at suitable intervals. The supporting insulator is slipped onto the unit in place between two loops in each parallel portion, the portions springing slightly together as the insulator is forced over loops in the desired position. tangular spacing insulators 33 are then inserted, one from each side, in the insulator between the parallel portions of the heating element where they are held together by a bolt passing therethrough. The spacing insulators likewise hold the portion of the heating element against opposite sides of the square hole in the supporting insulator, thus preventing the supporting insulator from slipping in either direction over the loops. Transverse projecting portions 34 are provided on the outer ends of the spacing insulators for the purpose of preventing them from slipping entirely through the supporting insulator. Obviously spacing clamps 21 may be used instead of spacing insulators 33.

The terminals of the heatin units are connected as desired by means 0 clamps 24. These clamps are carried on a framework comprising two parallel metallic supporting strips 25 having a plurality of transverse bars 26 and 27 connected thereto by means of spacing blocks 28. The blocks 28 are attached at spaced intervals to the strips 25 by screws or bolts, while the ends of the transverse bars 26 and 27 are attached by means of bolts to opposite sides of the blocks in alternate relation. The bars 26 may be somewhat heavier in construction than the bars 27 for the reason that they carry the terminal clamps 24. The supporting strips 25 are attached to the boiler by bolts or rivets so as to hold the framework in chamber 16 directly in front of the tubes with the transverse bars 27 each across a series of adjacent tubes and the transverse bars 26 each between series of tubes. The transverse bars 26 and 27 are made of suitable insulating material having the necesary strength.

The terminals of each unit protrude from Recthe tube on each side of a transverse insulating bar 27 which prevents contact between them. As shown in Fig. 1, the heating are connected in series in groups 0 four, the terminals (1, b, 0, (Z, c, and of the groups projecting through insulating tubes 33 in the shell of the boiler. Adjacent terminals, as shown in Fig. 3, are electrically connected together between the two pieces of electrically conducting material of clamps 24:. The clamps are held together, and to the transverse bars 26 by a strap 29 surrounding the bar, by means of bolts 30 passing therethrough. The groups of units are divided into two sections of three groups, the groups in the sections being connected in Y by conductors 31 and 32. I

A similar set of heating units, connected inlike manner in groups and sections, is mounted in the left hand side of the boiler. These units are energized through terminals a, b, 0', d, e, and f.

When the apparatus is in operation, the terminals of each section are connected through suitable switches or contactors to a three phase source of alternating current so as to energize the sections of the heater and rapidly raise the temperature Of the boiler. Preferably, the sections of the heater will be connected to the supply source in succession, and disconnected in a like manner, in order to prevent excessive disturbance in the supply source due to sudden application or disconnection of load. Obviously, during periods of low steam consumption it ma benecessary to energize only a part of tie sections of the heater to generate the required amount of heat.

By means of well known standard safety devices, the boiler may be automatically supplied with water, and the heater automatically connected and disconnected to the supply source in response to the steam pressure so that the entire procem of generating steam in accordance with my invention becomes automatic. No attention, therefore, is necessary with the exception of daily blowing off and occasional observation.

The heating units may be interconnected into groups and the groups into sections in any suitable manner to conform to the voltage, phase and other characteristics of the suppl source: Since the heating operation oes not depend upon induction, alternating current of any frequency may be used and direct current may be used as well. In the heating of a long boiler, it may be advantageous to insert the heating units from each end; in this arrangement the length of the heating unit is one half the length of the tube.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention together with the apparatus which I now consider to units I re resent the best embodiment thereof, but I esire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. What I claim as new and desire to se cure by Letters Patent of the United States, 1s:

1. A self contained electric heating unit consisting of a self-supporting stri of resistance material bent in the form 0 a hairpin, and provided with spacing and supporting insulators intermediate the lengthmaterial having substantially parallel portions provided 'with intermediate spacing and supporting insulators, whereby the units can be slid into the tubes of the boiler and supported therein on the insulators.

3. The combination with a fire tube boiler, of aplurality of self contained heating units, each unit consisting of a strip of resistance material bent in the shape of a hairpin and provided with intermediate spacing and sup porting insulators, whereby the units can be independently slid into the tubes of the boiler and supported therein on the insulators, and means for electrically interconnecting said units. i

In witness whereof, I have hereunto set my hand this 1st day of April, 1921.

ALBERT N. oTIs'. 

